FIG. 1 is a plan view of a state-of-the-art aircraft 10 which comprises a fuselage 12, on either side of which is fixed a wing 14a-b which supports one or more engine(s) 16a-b. 
To the rear, the aircraft 10 likewise comprises a horizontal stabilizer 18a-b which is rotatable about a horizontal axis and which extends on either side of the fuselage 12. A horizontal stabilizer of this kind is referred to as an adjustable horizontal stabilizer (AHS).
The aircraft 10 likewise exhibits, mounted on either side of the fuselage 12 and on the adjustable horizontal stabilizer 18a-b, an elevator 20a-b which is rotatable about a horizontal axis and which is positioned on the trailing edge of the adjustable horizontal stabilizer 18a-b. The elevator 20a-b is fixed to the adjustable horizontal stabilizer 18a-b by a hinge.
The aircraft 10 likewise comprises a vertical stabilizer 22 at the rear of which a rudder 24 is movably mounted about a vertical axis.
The adjustable horizontal stabilizer 18a-b is operated by an actuator and ensures the long-term trim of the aircraft 10. Each elevator 20a-b is likewise operated by one or more other actuators and ensures the short-term trim of the aircraft 10, as well as maneuvers of the aircraft 10.
When an elevator 20a-b is deflected upwards, it reduces the stalling incidence of the adjustable horizontal stabilizer 18a-b. This stalling incidence plays an important part during a dive maneuver (manual) of the aircraft 10 in re-establishing speed and the reduction in the stalling incidence leads to an increase in the size of the adjustable horizontal stabilizer 18a-b to balance out the effects of this reduction.
Moreover, the deflection of the elevator 20a-b generates a large variation in the hinge moment on the adjustable horizontal stabilizer 18a-b and therefore a strong axial force on the actuator operating the adjustable horizontal stabilizer 18a-b. 
In order to balance these elements, it is then necessary for the adjustable horizontal stabilizer 18a-b and each actuator to be oversized, which has an impact on the weight and volume of the equipment and on its energy needs.